GENERAL

My goal was to create a device that can, autonomously, take advantage of dynamic, variable electrical power rates, such as those from Tibber.com (i.e., the cheapest hours!). The starting point is that the device to be controlled can easily be turned on and off, that it should be turned on for a limited time during the day, and that it doesn't matter when during the day the device is turned on. One might think of:

• a water heater
• a dishwasher
• a washing machine
• a rechargeable car
• a rechargeable (bike) battery

The second and third cases present specific problems because such devices usually cannot be easily turned on as they are set up via software. I have therefore initially focused on the first case: a water heater (for which the simple rule is that applying voltage means heating (to the desired temperature), and turning off the power means not heating).

I built the system (I call it a "Tibber timer") into an old (mechanical) timer clock because then I can easily plug it into a socket and the controlled device into the timers socket. For this purpose, a Dhiel Diletta/Multimat timer is well suited. The mechanical clockwork was, of course, first removed; the original dial disk is replaced by a flat disk: in the middle of that disk, a small LED will be placed to provide information about the starting and functioning of the Tibber timer. I prefer this setup over a home automation solution because I don't need lamps that turn on automatically and other "smart" actions. (if you call "if this then this else that" smart)

The whole consists, besides the housing, of the following:

• a Raspberry Pi Pico with Wi-Fi
• a relay (for by example 2000 Watt)
• a Hall current sensor
• a small 5 Volt power supply

Wifi is needed to retrieve the hourly rates for the electrical power for the following day from the Tibber.com website. I specifically chose Tibber because it has an excellent interface to their database. (no hassle with a webscrobbler)

The Tibber timer further communicates with the outside world via the MQTT protocol. It reports its functioning and offers the possibility to influence its operation (remotely), for example, if you want to turn the device off permanently. The user is free to ignore the output. A user does not need to give commands either. There are many ways to communicate with MQTT devices, for example, using Android MQTT apps. I use the output of the Tibber timer to create a log file of the controlled device. See below.

The current sensor measures the power used and thus also the savings by using the cheaper hours. With the current sensor, I also create a power profile of the device to be controlled, i.e., how long it is usually on. That also determines the most favorable moment for it to be turned on.

The power supply provides the Raspberry Pico and the relay with power from the 230 Volt. Because of spikes in the power supply (due for example to the relais) it may be necessary to put an Elco (of for example 4700 micro Farad) parallel to the 5V power supply.

LOGFILE

Below is a part of the logfile for my boiler:

2023-04-15 10:39:14 ============================
2023-04-15 10:39:14 Starting Tibber program 1.33
2023-04-15 10:39:14 ============================
2023-04-15 10:39:14 Connected on Asus-xxx4
2023-04-15 10:39:14 IP addresses 10.0.0.247 255.255.255.0 10.0.0.138 10.0.0.138
2023-04-15 10:39:14 MQTT Commands from DenHaag/xxxxxxxx/Boiler/in/#
2023-04-15 10:39:14 MQTT Publications on DenHaag/xxxxxxxx/Boiler/out/#
2023-04-15 10:39:14 Fetching Tibber data from site (in Eurocents)
2023-04-15 10:39:17 Today 32.4 31.0 31.3 30.5 30.1 30.0 30.2 30.1 30.3 29.7 28.9 28.8
26.8 19.2 17.5 24.8 26.2 29.4 31.0 33.5 33.7 32.9 32.9 31.9
2023-04-15 10:39:19 Length tomorrow data 0
2023-04-15 10:39:19 Tomorrow taken from today
2023-04-15 10:39:19 Starts at 13:00 Stops at 17:00 ( 8460 22860 seconds)
2023-04-15 10:39:19 Fetching again in 10 hours
2023-04-15 13:01:15 Turning relais on
2023-04-15 17:01:14 Turning relais off
2023-04-15 20:39:19 Energy (kWh) in window: 2.300 and outside window: 0.000
2023-04-15 20:39:19 Costs in window: 0.427 otherwise: 0.674
2023-04-15 20:39:19 Mean tarif : 0.293 profit : 0.246
2023-04-15 20:39:19 Fetching Tibber data from site (in Eurocents)
2023-04-15 20:39:23 Today 32.4 31.0 31.3 30.5 30.1 30.0 30.2 30.1 30.3 29.7 28.9 28.8 26.8 19.2 17.5 24.8 26.2 29.4 31.0 33.5 33.7 32.9 32.9 31.9
2023-04-15 20:39:26 Tomorrow 30.9 30.0 29.8 29.6 29.8 30.0 30.0 29.9 30.8 31.3 30.9 30.5 30.0 29.3 28.9 28.8 29.0 29.6 31.4 33.5 34.4 33.8 33.1 32.6
2023-04-15 20:39:26 Starts at 14:00 Stops at 18:00 (62460 76860 seconds)
2023-04-15 20:39:26 Fetching again in 24 hours
2023-04-16 14:00:57 Turning relais on
2023-04-16 18:00:57 Turning relais off\

INSTALLATION

The software of this project consists of some python files. some text files and a json file. You must upload the files to the raspberry pico. This can easily be done by THONNY (on your PC) and a usb cable to your raspberry pico. The json file is very important because it determines how the Tibber timer is configured and will work.

The Json file consists of:

• wifi data
• mqtt data
• tibber data
• timeserver data
• devices data

Most data is obvious; the "devices data" needs some explanation:

• tibbertype: can be NO, NC, AO, AC deteremines how the relais works
• initmode: can be tibberon. Anything else and the device will not automatically work
• relaispin: the pin that the relais is connected to
• ledpin: the pin of the pico on which the led is connected
• ledvalue: controls the blinking of the led
• ac712: data concerning this current measuring device
  • adcpin: the pico pin to which the analog out of the ac712 is connected
  • powercorr: a correction factor for the ac712
  • treshold: ignore power usage below this treshold

CONNECTION

The Tibber timer needs an usb port to connect the pico to your PC (running for example Thonny)

A small power supply is needed for the pico and the relais that turns your controlled device on and of.

A small relais must be connected to the pico. The on/off output of this relais must be used to switch on/off your device. The relais is configured with the tibbertype line in the json file: NO (normally open), NC (normally closed) and AO and AC (always open closed). A hall current sensor is connected in series with this relais. The relais must off course be up to the task to turn your device on and off. The used current sensor is not really necessary but can give you an idea of how much money is saved (don't expect to get rich). The sensor also measures how long your device is "normally" on: this is important to calculate the optimum time interval. You can see the values of the profile of your device by giving the profile command. The current sensor is not very accurate, therefore a correction factor and a treshold value in the json file.

USAGE

When you connect your Tibber timer to your power socket the first thing the program (main.py) does is reading your json file. About 8 steps are taken: after every step the led blinks once. If everything is OK the led will blink thereafter once every 15 seconds. If the device is turned on (in the following hours) the led will blink twice every 15 seconds. It is problably best to test the json file with the timer connected to your PC (and the Tibber timer not in a power socket): Thonny will show possible errors in the json file. You can check the format of your json file for example with the jq command or any other json lint program. The MQTT output may also be helpfull in debugging the json file. Depending on the time of day and thus the availability of the hourly pricing data of the next day, the first window calculated might actually the window be off and wrong. You can reboot your Tibber Timer somewhat later (in case of tibber.com after 12 o'clock). Normally the calculating of the next window occurs between 20:00 and 21:00 .

OUTPUT

The Tibber Timer gives status information about its functioning to the MQTT broker as defined in the json file. You can ignore this information but it may be helpfull.

INPUT

You can give input commands to the device by means of MQTT commands. You can give these commands on your PC for example whith mqtt-explorer or in a linux shell with an appropriate command. The list of commands is in the help.txt file on your pico. This file shown with the MQTT command "help".

BOOTLOG FILE

The Tibber timer is supposed to run permanently: it does not need reboots. If it reboots (for whatever reason) this is written to the bootlog.txt file. When going on holiday you can turn off your device with the command: neveron. If your device reboots during a holiday wherein you don't want your device (for example a boiler) to work you can use the initmode : neveron line in the json file. After return from your holiday you can check for possible reboots and then turn your device on with the command: tibberon. you can see the status with the status command.

OVERRULING THE TIBBER TIMER

This all works a bit tricky. Two commands turndeviceon and turndeviceoff work at the same level as the commands used in the timer window (start and stop time). If you use these commands in or near the set window the result maybe not as expected: if you issue the turndeviceon command right before the stop time of the set window, the device is turned on for a short time. More easy is using the commands: alwayson and neveron. After using neveron you must, normally, issue the command tibberon.

DIFFICULT DEVICES

A boiler can often simply be turned on and off. Unfortunately many manufacturers think the world is waiting for there "smart" devices. At best you can turn such device simply on or off by means of a local (in your smart device) offered website of the device. At worst you must use your phone that doubles as a glorified remote control (how you must control this handy app from your Tibber Timer is un clear). Sometimes you can program your device at your convenience and then , later , push a button. You could try to make the connection of this button yourself and connect this to the relais of your Tibber timer. Otherwise you can use a mechanical device to pushes this button (for example a fingerbot). If the manufacturer thinks he is really smart this button must be pushed shortly after the programming of the device (or the device goes to an error situation with a nice impressive error code). An other possibility is to use a doorlock for starting the device. That is by making or braking a wire in the doorlock (use the relais settings NO and NC). I use this method with my dishwasher. My washingmachine has no means to start it remotely but when the power is cut shortly after starting the machine it will later continue at that point. There is a command pulse for the Tibber Timer that you can use to program your device and then cut the power.

DAYLIGHT SAVING TIME

The transition from summertime to wintertime does not go automatically (I found that unnecessary). If you give the settime command the time is corrected but at that day the turn on/off times will be an hour off. The next day everything should be OK.

SPECIAL VERSIONS OF THE TIBBER TIMER

I made two special versions of this device: one with a small TFT screen and one that will log the power usage of the attached device for one day to make a usage profile of the device. The one with the TFT screen is best used with a better current measurement device and shows every minute the real and apparent power, phase angle and voltage/current. Because of space limitations there is no relais and the Tibber functionality is not present.